MOSCOW -- It began in the blazing heat and choking dust of the southern Russian summer, as hundreds of thousands of cocky German soldiers smashed their way into Stalingrad, intent on making that great industrial center on the banks of the Volga River the graveyard of Soviet resistance.

It ended 50 years ago today, in the bitter chill of winter, as the last ragged, starving survivors of that once-powerful army staggered out of their bunkers amid the rubble of the broken city and surrendered.

During the five months that they fought each other in Stalingrad, German and Soviet soldiers turned the city into a smoldering, corpse-littered ruin.

They fought battles of unparalleled intensity, at such close quarters that they sometimes fought each other for days on end from different floors of the same building.

And when it was over, something quite basic had been decided. The German drive to sever Russia's main inland waterway and to cut off its oil supplies had failed. Adolf Hitler's war machine, which had rolled over vast stretches of Europe so effortlessly during the first three years of World War II, had been stopped -- as it turned out, for good. After Stalingrad, the road for the Germans led only backward.

But it was a near thing -- at one point, the main force of Soviet defenders was pushed back to within 100 yards of the Volga.

"If they had thrown us into the Volga, they would have taken over the Stalingrad steppes and gone all the way to Moscow," says Pyotr Shogin, 70, a pensioner who was an artillery sergeant in the great battle. "There's no way to stop tanks on the steppes. But we managed to hold our positions. Those friends of ours who died for Stalingrad prevented a great tragedy."

The cost of the victory was enormous -- much greater than the Kremlin admitted at the time. A new study by Russian historians reveals that Soviet casualties at Stalingrad totaled 1.1 million.

Yet the German losses, while numerically smaller, were in relative terms even greater. An entire army group of 330,000 men, veterans of the great victories in Poland, France and the early days of the Russian campaign, died or surrendered at Stalingrad. Twenty-four German generals, including one field marshal, Friedrich von Paulus, were captured. At Stalingrad, most historians agree, the Wermacht suffered a blow from which it never recovered.

Curiously, it was neither apparent nor inevitable that Stalingrad would become such a pivotal encounter. The main objective of the German armies operating in southern Russia during 1942 was to capture the rich oil fields of the Caucasus and cut the vital rail and water links that connected the northern and southern parts of the Soviet Union. Stalingrad became the focal point of the campaign almost by accident.

"The Germans probably could much more easily have cut the Volga lifeline at any point to the south of Stalingrad," wrote historian Isaac Deutscher. "It was mainly a psychological motive that now impelled Hitler."

That motive was connected partly to the name of the city, changed from its original Tsaritsyn in 1928 to commemorate Soviet leader Josef Stalin's participation in a battle fought there during the Russian Civil War. (During the de-Stalinization campaign of the 1960s, the name of the city was changed again, to its present Volgograd.)

Beyond the name of the city, the sheer stubbornness of its defenders seemed to obsess Hitler.

His armies had reached the brink of Soviet Russia's two greatest cities, Moscow and Leningrad, the previous year, only to be turned aside, and the Nazi leader was determined to avoid a similar fate at Stalingrad.

In August and early September 1942, 21 German divisions launched an all-out offensive. By mid-September the Soviets had to evacuate most of their artillery to the east bank of the Volga.